Method for drying porous wallboards



June 2, 1942. l G. v. HOLM 2,284,838

- METHOD Fon DRHNG PoousI wALLBoARDs Filed dgn. a; 193e 2 shuts-sheet 1 En ATTORN -EY June 2, 1942. G. v. HoLM 2,284,333

Mm-aon Fon 1mm@ Ponous wALLoAnns Filed Jan. '8. 193s l2 sneetssneet 2 Patented June 2, 1942 METHOD FoaD WALLB RYING 'POROUS OARDS Gustav Valdemar holm, Stockholm, Sweden ApplicationJanuary 8, 1938, Serial No. 184,013 A In Sweden January 11, 1937 1 claim. (CLM-1stv The present invention relates to a method for drying porousy Wall boards.

One object of the invention is to provide a method for drying porous wall boards' whereby the drying is effected rapidly and uniformly.

vAnother object of the invention is to devise a drying method in which the wall boards are dried rapidly with a relatively small expense of energy.

Still anotherobject of the invention is to dry wet porous Wall boards rapidly without any 'danger of the'boards becoming deformed or their pores being closed during the dryingoperation.

The above mentioned and other objects which will appear more clearly as the specification proceeds, are accomplished according to the present invention, in the `manner set forth in the following detailed description and defined in the appended claim.

According to the invention, the drying operation is carried out in two steps. The first part of the drying is effectedv by supplying heat exidly cooled by passing cold air through the pores. If the cooling air is moistened in any suitable 'Y manner, the driedboards may be given any de- ;sided moisture content to prevent subsequent shrinkage or swelling of the boards.

In order to make the invention more fully`- understood, a drying apparatus for carrying out -the drying methodaccording to the invention is illustratively exemplified in the accompanying drawings in which;

Fig. 1 is a vertical longitudinal section through the drying apparatus, some parts being shown in o side elevation.

clusively to the surfaces of the boards without substantially heating the interior thereof until sufilcient water has been removed fromv the pores of the board to substantially reduce the resistance to the flowof air through said pores,

and the drying is subsequently completed byv passing drying air through the pores from one `surface of the board to the opposite surface' thereof.

Al complete rapid drying of a porous wall board can be accomplished only, if drying air is passed through the pores `of the board to remove the water containedA in such pores. boards are to be dried exclusively by forcing drying air'through their pores, an exorbitant amount l of energy must be expanded, because the wet board offers a very high resistance to van air current to be passed through its pores.

However, if the Figs. 2, 3 and 4 are substantially transverse sections taken, respectively, on lines II-II, III- IlI and IV-IV of Fig; 1, and l Fig. -5 is a partial longitudinal section illustrating a modification of the heating elements in the left-hand portion of the device shown in Fig. 1. Referring now to the figures and rst` to Figs. 1 and 2, the' drying apparatus is divided into two housingsl and 2. The housing i serves for sweeping the surfaces of the boards C with hot air, and, in the housing 2, a drying medium is passed through the poresof the boards C.

'The boards C are introduced into the drying chamber 5 of the housing l, at the left hand end thereof, for instance by hand. The boards C are fresh air and exhaust openings 2| for moist air -Applicant found that the magnitude of this l resistance depends to a substantial degree upon the Water content of the board and decreases as the water content is reduced.

' By providing a drying method in which, during the first part of the drying, heat is supplied exclusively to the surfaces of the board, and, subsequently, an air current is passed through Athe pores of the board from one surface to the opposite surface thereof, applicant effects a rapid, uniform and complete drying of the boards with a minimum expense of energy. Moreover,

in applicants drying method, the pores of the board are kept open, so that the boards, after completion of the drying operation, may be rapare provided in the side Walls of the housing l. Heat is supplied to the surfaces of the boards C in the form of hot air discharged from perforated pipes 6 connected to a hot air manifold 6|.

Instead of using hot air, the surfaces of the boards C may be swept with drying heat radiating from electrically heated plates 'l arranged immediately below and in spaced relationship above the rollers 3 supporting the boards C, as shown in Fig. 5.

In the housing 2, the boards are supported on perforated sheet metal screens i8 which permit the passing of drying air through the boards.

i As seen in Figs. 3 and 4, transversely inclined partitions 9 are arranged in the housing 2 to` I8 into two half-compartments Ita and |317 communicating with each other through the perforations of the.screen. Each compartment I3 can `be closed by means of ap'doors provided at its opposite ends, only the ilap doors |3| at the left hand entrance ends of the compartments Il being visible in Fig. 1.

'I'he boards C are moved into and discharged from the compartments I3 by means of transverse rollers |32 disposed adjacent the entrance and the exit, respectively, of each compartment and driven through pulleys |33 and belts |36 from a motor |35.

The drying air circulates transversely through the compartments I3 in the direction indicated by the arrows in Fig. 3 and passes from one side of the vhousing 2, where it is Aguided upwardly4 in a manifold I0, into the half compartments |3a, then downwards through the boards C and screens I8 into the half compartments |3b and into a manifold o'n the opposite side of the 'housing 2 where it is led downwardly into the yreturn ducts |2a, |2b disposed below the drying compartments Il.

Each of the return ducts I2a and I2b has arranged therein a fan I4 and a heating device l5 which heats the circulating air.

The housing 2 may also be used for cooling the' boards, and, for this purpose, the air portion passing through the duct |2b at the discharge end of the housingz may be given a suitable low temperature.

Additionally, the humidity of the air within the housing 2 may be varied by means of water spraying nozzles I8 and humidifying surfaces I7 in the duct |27) (see Fig. 4).

Having now described my invention, what I' the drying by passing drying air through said.

pores from one surface of the board to the opposite surface thereof.

GUsTAv VALDEMAR HoLM. 

